Oncogenic β-catenin-driven liver cancer is susceptible to methotrexate-mediated disruption of nucleotide synthesis

Background:Liver cancer is largely resistant to chemotherapy.This study aimed to identify the effective chemotherapeutics forβ-catenin-activated liver cancer which is caused by gain-of-function mutation of catenin beta 1(CTNNB1),the most frequently altered proto-oncogene in hepatic neoplasms.Methods:Constitutiveβ-catenin-activated mouse embryonic fibroblasts(MEFs)were established by deleting exon 3(β-catenin^(Δ(ex3)/+)),the most common mutation site in CTNNB1 gene.A screening of 12 widely used chemotherapy drugs was conducted for the ones that selectively inhibitedβ-catenin^(Δ(ex3)/+)but not for wild-type MEFs.Untargeted metabolomics was carried out to examine the alterations of metabolites in nucleotide synthesis.The efficacy and selectivity of methotrexate(MTX)onβ-catenin-activated human liver cancer cells were determined in vitro.Immuno-deficient nude mice subcutaneously inoculated withβ-catenin wild-type or mutant liver cancer cells and hepatitis B virus(HBV);β-catenin^(lox(ex3)/+)mice were used,respectively,to evaluate the efficacy of MTX in the treatment ofβ-catenin mutant liver cancer.Results:MTX was identified and validated as a preferential agent against the proliferation and tumor formation ofβ-catenin-activated cells.Boosted nucleotide synthesis was the major metabolic aberration inβ-catenin-active cells,and this alteration was also the target of MTX.Moreover,MTX abrogated hepatocarcinogenesis of HBV;β-catenin^(lox(ex3)/+)mice,which stimulated concurrent Ctnnb1-activated mutation and HBV infection in liver cancer.Conclusion:MTX is a promising chemotherapeutic agent forβ-catenin hyperactive liver cancer.Since repurposing MTX has the advantages of lower risk,shorter timelines,and less investment in drug discovery and development,a clinical trial is warranted to test its efficacy in the treatment ofβ-catenin mutant liver cancer.